Sheet carrying method for sheet finishing device

ABSTRACT

A sheet finishing device includes: a housing unit which houses a sheet discharged from an image forming apparatus; a carrying unit which carries the sheet discharged from the image forming apparatus in a direction of the housing unit; a standby unit which is arranged on a carrying path of the carrying unit and temporarily holds the sheet; a finishing unit which is arranged on the carrying path of the carrying unit and performs finishing of the sheet; and a control unit which, when a carrying error in the carrying unit is a first error, controls the carrying unit to stop and responses the first error to the image forming apparatus, and when the carrying error is a second error, controls the carrying unit to continue driving and responses the second error to the image forming apparatus.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Provisional U.S. Application 61/150,267 filed on February 5, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a sheet finishing device which finishes a sheet having an image formed thereon by an image forming apparatus such as a copier or MFP (multi-functional peripheral).

BACKGROUND

There is a sheet finisher which performs finishing such as stapling and bundle carrying of sheets discharged from an image forming apparatus. In the sheet finisher, while a sheet is carried to a finishing unit or a paper discharge tray, a timing error may occur which is caused by a delay in carrying the sheet or a delay in finishing due to the difference in paper quality among various sheets and so on. In order to resume the sheet finisher and the image forming apparatus that are stopped by the timing error, the user must remove the sheet left in the sheet finisher or the image forming apparatus even though the sheet is not damaged. Moreover, it is difficult to remove the sheet left in the sheet finisher or the image forming apparatus, and maintenance of these devices takes time. What is more, the sheet that is not damaged in the first place may be wasted.

Thus, there is demand for a sheet finisher in which, when a timing error occurs while a sheet is being finished, the user's operation to remove the sheet is reduced, maintenance performance is thus improved, and no sheets are wasted.

SUMMARY

According to an aspect of the invention, a sheet finishing device includes: a housing unit which houses a sheet discharged from an image forming apparatus; a carrying unit which carries the sheet discharged from the image forming apparatus in a direction of the housing unit; a standby unit which is arranged on a carrying path of the carrying unit and temporarily holds the sheet; a finishing unit which is arranged on the carrying path of the carrying unit and performs finishing of the sheet; and a control unit which, when a carrying error in the carrying unit is a first error, controls the carrying unit to stop and responses the first error to the image forming apparatus, and when the carrying error is a second error, controls the carrying unit to continue driving and responses the second error to the image forming apparatus.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the configuration of a sheet finisher connected to an MFP according to an embodiment;

FIG. 2 is a schematic view showing the configuration of the sheet finisher according to the embodiment;

FIG. 3 is a schematic perspective view showing a part of finisher unit according to the embodiment;

FIG. 4 is a schematic plan view showing standby trays according to the embodiment;

FIG. 5A is a schematic block diagram showing the control system of the sheet finisher according to the embodiment;

FIG. 5B is a schematic explanatory view showing a part of a response format to be response to the MFP from a finisher control circuit according to the embodiment;

FIG. 6 is a schematic explanatory view showing the occurrence of a paper jam error according to the embodiment;

FIG. 7 is a schematic explanatory view showing the occurrence of a timing error due to a delay in discharging a sheet bundle according to the embodiment;

FIG. 8 is a schematic explanatory view showing the occurrence of a timing error due to a delay in rotation of an assist arm according to the embodiment;

FIG. 9 is a flowchart showing a process when a timing error occurs, according to the embodiment;

FIG. 10 is a schematic explanatory view showing a sheet in the MFP when a bundle discharge timing error occurs, according to the embodiment;

FIG. 11 is a schematic explanatory view showing a sheet buffered to a standby tray after a bundle discharge timing error occurs, according to the embodiment; and

FIG. 12 is a schematic explanatory view showing the continuation of carrying a next bundle according to the embodiment.

DETAILED DESCRIPTION

An embodiment will be described hereinafter. FIG. 1 is a schematic view showing the configuration of a multi-functional peripheral (MFP) 10 as an image forming apparatus according to the embodiment, and a finisher 20 as a sheet finishing device connected to the MFP 10. The finisher 20 is connected to a lateral side of the MFP 10 via a relay unit 60. In the MFP 10, a printer unit 11 forms an image on a sheet P and the sheet P is discharged from a paper discharge roller pair 12 to the finisher 20 via the relay unit 60. The MFP 10 has a scanner 8 and a control panel 14 having a display panel 14 a, in an upper part of the printer unit 11. The MFP 10 has a pickup roller 17 which takes out a sheet P from a paper supply unit 16.

The finisher 20 has, for example, a stapler 56 which staples sheets as a finishing unit, as shown in FIG. 2. The finisher 20 is carries the sheet P, discharged from the paper discharge roller pair 12 of the MFP 10 and relayed by the relay unit 60, to a first tray 21 or a second tray 22 as a housing unit. The finisher 20 has a first carrying mechanism 23 which carries the sheet discharged from the paper discharge roller pair 12 in the direction of the first tray 21, and a second carrying mechanism 24 which carries the sheet P discharged from the paper discharge roller pair 12 in the direction of the second tray 22, as a carrying unit.

The first carrying mechanism 23 has an entrance roller pair 26 and a first exit roller pair 27. The second carrying mechanism 24 has a first path 31 for carrying the sheet P in the direction of the second tray 22 via the entrance roller pair 26, a second exit roller pair 28, and a standby tray roller pair 30 on the exit side of standby trays 32 a and 32 b. The second carrying mechanism 24 has a second path 41 for carrying the sheet P in the direction of the second tray 22 via the entrance roller pair 26, the second exit roller pair 28, the standby trays 32 a and 32 b, and a processing tray 50.

The finisher 20 has the processing tray 50 as a supporting unit which constituting the finishing unit and supports the sheet P at the time of finishing, and lateral alignment boards 51 and 52 which align the sheet P on the processing tray 50 in the lateral direction parallel to the direction of the width of the sheet P, as shown in FIG. 3. Lateral alignment motors 51 a and 52 a drive the lateral alignment boards 51 and 52, respectively, to reciprocate in the direction of the width. The finisher 20 has, as the finishing unit, a paddle mechanism 54 which aligns the sheet P on the processing tray 50 in the longitudinal direction orthogonal to the direction of the width of the sheet P, and the stapler 56 which staples the sheet on the processing tray 50.

The paddle mechanism 54 is rotated about a paddle shaft 55 by a paddle motor 55 a. The paddle mechanism 54 has sheet receivers 54 a, short paddles 54 b, and long paddles 54 c. When the paddle mechanism 54 rotates, the short paddles 54 b strike the sheet P toward the processing tray 50 and the long paddles 54 c move the sheet P toward the stapler 56. A stapler shift motor 56 a reciprocates the stapler 56 in the direction of the width. A stapler motor 56 b drives the stapler 56 for stapling.

On the processing tray 50, the sheet P falling directly from the second exit roller pair 28 or via the standby trays 32 a and 32 b is placed. The finisher 20 has rear edge stoppers 57 and longitudinal alignment rollers 58 to the rear edge side in the carrying direction of the sheet P on the processing tray 50, and has discharge rollers 59 to the forward edge side in the carrying direction of the sheet P on the processing tray 50. A longitudinal alignment motor 80 drives the longitudinal alignment rollers 58.

A timing belt 72 is laid over a roller shaft 58 a of the longitudinal alignment rollers 58 and a roller shaft 59 a of the discharge rollers 59. The longitudinal alignment motor 80 drives the discharge rollers 59 via the timing belt 72. The sheet P placed on the processing tray 50 has its rear edge in the carrying direction regulated by the rear edge stoppers 57 and is longitudinally aligned sequentially by the longitudinal alignment rollers 58, the discharge rollers 59 and the paddle mechanism 54.

The finisher 20 has a bundle pawl belt 70 having a bundle pawl 70 a. A bundle pawl motor 81 drives the bundle pawl belt 70. The second carrying mechanism 24 has a pair of ejectors 71 a and 71 b which push out a finished sheet bundle T on the processing tray 50. As an ejector clutch 82 is turned on, the ejectors 71 a and 71 b are connected to the bundle pawl motor 81 which drives the bundle pawl belt 70. At the time of discharging the sheet bundle T on the processing tray 50, the discharge rollers 59 and the bundle pawl belt 70 are driven after the ejector clutch 82 is turned on.

The discharge of the sheet bundle T on the processing tray 50 is first started by the ejectors 71 a and 71 b and the discharge rollers 59. After that, the bundle pawl 70 a of the bundle pawl belt 70 coming with a delay overtakes the ejectors 71 a and 71 b and receives the sheet bundle T. Then, the bundle pawl 70 a and the discharge rollers 59 discharge the sheet bundle T to the second tray 22. When the ejector clutch 82 is turned off, the ejectors 71 a and 71 b return to the discharge start position of the sheet bundle T.

The standby trays 32 a and 32 b are divided in two in the direction of the width of the sheet P, as shown in FIG. 4. The standby trays 32 a and 32 b are moved synchronously with and in the opposite directions to each other by a link mechanism 36 including racks 33 and a pinion gear 34. At the time of standby, the standby trays 32 a and 32 b are positioning to support both sides of the sheet P.

At the time of carrying the sheet P, the standby trays 32 a and 32 b open in the direction of the width and drop and carry the sheet P onto the processing tray 50. The finisher 20 has assist arms 37 which regulate the movement of the sheet P on the standby trays 32 a and 32 b. The distal ends of the assist arms 37 hang down in the direction of the standby trays 32 a and 32 b because of the energizing force of springs 38. The assist arms 37 are energized, for example, by a link mechanism 37 b rotated by a stepping motor 37 a, and the assist arms 37 rotate in the direction of arrow f away from the standby trays 32 a and 32 b. The standby trays 32 a and 32 b and the assist arms 37 constitute a standby unit.

The sheet receivers 54 a of the paddle mechanism 54 support the rear edge of the sheet P on the standby trays 32 a and 32 b. While receiving the sheet P onto the standby trays 32 a and 32 b from the second exit roller pair 28, the assist arms 37 are energized by the link mechanism 37 b, thus the assist arms 37 rotate in the direction of arrow f, and move away from the standby trays 32 a and 32 b as indicated by the double chain-dotted line in FIG. 2.

When the reception of the sheet P on the standby trays 32 a and 32 b is finished, the energization of the assist arms 37 by the link mechanism 37 b is released and the assist arms 37 hang down in the direction of the standby trays 32 a and 32 b because of the energizing force of the springs 38. By handing down in the direction of the standby trays 32 a and 32 b, the assist arms 37 restrains flexure and curling of the sheet P during standby. When dropping and carrying the sheet P to the processing tray 50 from the standby trays 32 a and 32 b, the assist arms 37 presses the rear edge of the sheet P toward the processing tray 50.

The finisher 20 has a first sheet sensor 76 which detects a paper jam in the first carrying mechanism 23, and a second sheet sensor 77 and a third sheet sensor 78 which detect a paper jam of the sheet P in the second carrying mechanism 24. The sheet sensors 76 to 78 detect that a paper jam is generated when the sheet sensors are not turned on even after the lapse of a predetermined time, or when, after the sheet sensors are turned on by the arrival of the sheet P, the sheet sensors are not turned off because of the failure of the rear edge of the sheet P to exit even after the lapse of a predetermined time.

Next, the control system of the finisher 20 will be described mainly with respect to the carrying of the sheet P. As shown in the block diagram of FIG. 5A, a finisher control circuit 90 as a control unit is connected to a CPU 95 which controls the entire MFP 10. The finisher control circuit 90 controls a stepping motor 37 a, the lateral alignment motors 51 a and 51 b, the paddle motor 55 a, the stapler shift motor 56 a, the stapler motor 56 b, the longitudinal alignment motor 80, the bundle pawl motor 81, the ejector clutch 82 or the like. The results of detection by the first to third sheet sensors 76 to 78 are inputted to the finisher control circuit 90.

The MFP 10 outputs various commands to the finisher control circuit 90. For example, the MFP 10 outputs a command to designate bundle discharge before starting sheet finishing, a pickup execution command at the time of starting printing, a command to notify of the passage of the sheet P through the final sensor, and the like, to the finisher control circuit 90. In response to these commands, the finisher control circuit 90 outputs responses to the MFP 10. The responses include, for example, a delay request to suspend printing and delay the supply of the sheet in the case of stapling at two positions, a stop request to stop printing when a paper jam of the sheet P occurs, and so on. When a timing error occurs, the finisher control circuit 90 responds to the MFP 10 by sending a delay request or a pickup stop request or the like in accordance with the content of the timing error. FIG. 5B shows a part of a response format 97 to response various kinds of information from the finisher control circuit 90 to the MFP 10. The response format 97 sets, for example, normality or abnormality of a command, an error code, a delay time in the case of a delay request, and the like.

When there is a delay request as a response from the finisher 20, the MFP 10 continues printing on the sheet P that is already taken out to the printer unit 11 from the paper supply unit 16, whereas the MFP 10 delays the takeout of a new sheet P by the pickup roller 17 by a predetermined time until the timing error is canceled.

When there is a pickup stop request as a response from the finisher 20, the MFP 10 stops the takeout of a new sheet P by the pickup roller 17, whereas the MFP 10 continues printing on the sheet P that is already taken out to the printer unit 11 from the paper supply unit 16 before the pickup stop request, and discharges the sheet P from the paper discharge rollers 12. By the way, when there is a pickup stop request from the finisher 20, the MFP 10 may also stop printing on the sheet P that is already taken out to the printer unit 11 from the paper supply unit 16 and only continues carrying the sheet in the direction of the paper discharge rollers 12.

When a paper jam error of the sheet P, which is a first error, occurs between the entrance roller pair 26 and the second exit roller pair 28, for example, as shown in FIG. 6, the finisher control circuit 90 stops the driving system of the finisher 20 and notifies the MFP 10 of the paper jam error and also notifies the MFP 10 of a stop request to stop printing. The notification of the paper jam error and the notification of the stop request are sent in the same response from the finisher control circuit 90 to the MFP 10.

In accordance with the response from the finisher control circuit 90, the MFP 10 displays the paper jam in the finisher 20 on the display panel 14 a and stops printing. After the finisher 20 and the MFP 10 are stopped, the user removes the sheets P in the finisher 20 and the sheet left in the MFP 10 and then restores the MFP 10.

When a timing error, which is a second error, occurs as shown in FIG. 7 or FIG. 8, the finisher control circuit 90 controls the driving system of the finisher 20 to continue and thus continues carrying the sheet P discharged from the MPF 10. Moreover, the finisher control circuit 90 sends the timing error and a delay request or a stop request as a response to the MFP 10. FIG. 7 shows the state when a timing error occurs as the discharge of the sheet bundle T from the processing tray 50 is delayed.

When the discharge of the sheet bundle T from the processing tray 50 is delayed, the finisher 20 delays the fall and carrying of the sheet P from the standby trays 32 a and 32 b to the processing tray 50 and continues carrying the sheet P discharged from the MFP 10 during this time, up to the standby trays 32 a and 32 b. FIG. 8 shows the state when a timing error occurs as the rotation of the assist arms 37 is delayed.

When the rotation of the assist arms 37 in the direction of arrow f is delayed, the finisher 20 continues carrying the sheet P discharged from the MFP 10, up to the first tray 21. The MFP 10 displays the discharge of the sheet to the first tray 21 on the display panel 14 a and prompts the user to remove the sheet P on the first tray 21.

Next, an example of the process of carrying the sheet P in the finisher 20 when a timing error occurs during bundle carrying will be described with reference to the flowchart of FIG. 9. After starting, in the finisher 20, the entrance roller pair 26 receives the sheet P discharged from the MFP 10 (ACT 100). The finisher control circuit 90 determines whether preceding processing is finished in the second carrying mechanism 24 (ACT 102).

For example, when buffering of the preceding sheet P to the standby trays 32 a and 32 b is still continued and the timing for the assist arms 37 to move away from the standby trays 32 a and 32 b is delayed as shown in FIG. 8 (No in ACT 102), the finisher control circuit 90 determined that there is a timing error in the assist arms 37 and proceeds to ACT 103. In ACT 103, the finisher 20 continues carrying the sheet P discharged from the MFP 10 toward the first carrying mechanism 23 instead of the second carrying mechanism 24 and discharges the sheet P to the first tray 21.

In ACT 103, the finisher control circuit 90 sends the timing error of the assist arms 37 and a pickup stop request as a response to the MFP 10. The MFP 10 stops takeout of a new sheet from the paper supply unit 16 by the pickup roller 17, whereas the MFP 10 continues printing on the sheet P that is already taken out from the paper supply unit 16 and discharges the sheet P from the paper discharge rollers 12. The MFP 10 also displays the discharge of the sheet to the first tray 21 on the display panel 14 a and notifies the user of the occurrence of the timing error. The finisher 20 discharges the sheet P on which printing is still continued, to the first tray 21, and ends the finishing. The user removes the sheet P from the first tray 21 and restores the MFP 10.

The sheet P that is already taken out to the printer unit 11, despite the delay in the rotation of the assist arms 37 and the resulting timing error, is not left in the MFP 10 but is carried to the first tray 21. Therefore, the user can release the timing error and restore the MFP 10 without carrying out maintenance to remove the sheet P in the MFP 10. The user' s operation to release the timing error can be reduced and maintenance performance can be improved.

In ACT 102, when the assist arms 37 are away from the standby trays 32 a and 32 b (Yes in ACT 102), the finisher 20 carries the sheet P toward the second carrying mechanism 24 and buffers the sheet P onto the standby trays 32 a and 32 b (ACT 106). The finisher control circuit 90 determines whether the number of the sheets P buffered on the standby trays 32 a and 32 b reaches a prescribed numbers of sheets (for example, 3 sheets) for the standby trays 32 a and 32 b. When the number of the sheets P buffered on the standby trays 32 a and 32 b reaches the prescribed numbers of sheets (Yes in ACT 107), the finisher control circuit 90 determines whether preceding processing on the processing tray 50 is finished (ACT 108).

For example, when the preceding sheet bundle T is being discharged from the processing tray 50 and the bundle discharge timing is delayed as shown in FIG. 7 (No in ACT 108), the finisher control circuit 90 determines that there is a bundle discharge timing error and proceeds to ACT 110. In ACT 110, the finisher 20 suspends the fall and carrying of the sheet P from the standby trays 32 a and 32 b to the processing tray 50. In ACT 110, the finisher control circuit 90 sends the bundle discharge timing error and a delay request until the sheet bundle T is discharged, as a response to the MFP 10. The MFP 10 suspends the takeout of a new sheet from the paper supply unit 16 by the pickup roller 17 and continues printing on the sheets P1 and P2 that are already taken out from the paper supply unit 16, as shown in FIG. 10 and FIG. 11.

The finisher 20 buffers the sheets P1 and P2 discharged from the MFP 10 onto the standby trays 32 a and 32 b until the bundle discharged of the preceding sheet bundle T from the processing tray 50 is finished. Therefore, there may be a case where a greater number of sheets than the prescribed number of sheets are buffered onto the standby trays 32 a and 32 b. As the bundle discharge of the preceding sheet bundle T on the processing tray 50 is finished (Yes in ACT 108), the standby trays 32 a and 32 b open in the direction of the width and drop and carry the buffered sheets P, P1 and P2 onto the processing tray 50, as shown in FIG. 12.

After the takeout of a new sheet by the pickup roller 17 is suspended in ACT 110 and is delayed by a predetermined time, the MFP 10 causes the pickup roller 17 to take out a new sheet P3 from the paper supply unit 16, as shown in FIG. 12, in order to resume printing.

In the case of continuing the bundle carrying on the processing tray 50, the finisher control circuit 90 adjusts the number of times of alignment on the processing tray 50 according to the number of the sheets P falling and carried from the standby trays 32 a and 32 b. In ACT 111, the finisher control circuit 90 determines whether the number of the sheets P to be aligned on the processing tray 50 is equal to or less than the prescribed number of sheets to be buffered on the standby trays 32 a and 32 b.

When the number of sheets to be aligned on the processing tray 50 is equal to or less than prescribed number of sheets (Yes in ACT 111), the finisher control circuit 90 sets the number of times of alignment to a prescribed number of times (ACT 112). The prescribed number of times of lateral alignment is, for example, one reciprocating movement of the lateral alignment boards 51 and 52 for a short-size sheet such as JIS standard A4 size, and two reciprocating movements of the lateral alignment boards 51 and 52 for sheets of other sizes than the short size.

The prescribed number of times of longitudinal alignment is, for example, two irrespective of the sheet size. That is, longitudinally aligned by rotating the paddle mechanism 54 twice for all of sheet. While the paddle 54 rotates twice, the longitudinal alignment rollers 58 are driven and therefore the time for longitudinal alignment by the longitudinal alignment rollers 58 becomes longer.

The sheet P on the processing tray 50 is aligned sequentially by the lateral alignment boards 51 and 52 and the paddle mechanism 54 (ACT 114). Then, when a sheet bundle T2 reaches a predetermined number of sheets (Yes in ACT 116), the sheet bundle T2 is discharged from the processing tray 50 to the second tray 22 (ACT 117) and the finishing ends. When the number of sheets to be aligned on the processing tray 50 exceeds the prescribed number of sheets in ACT 111 (No in ACT 111), the finisher control circuit 90 sets the number of times of alignment of the sheet P on the processing tray 50 to the prescribed number of sheets plus an additional number of times (ACT 113). The additional number of times is, for example, 1 to 2 both for lateral alignment and for longitudinal alignment. When a bundle discharge timing error is generated, as the number of times of alignment of the sheet P on the processing tray 50 is adjusted, the sheet P can be aligned satisfactorily despite the delay in falling and carrying of the sheet P from the standby trays 32 a and 32 b to the processing tray 50.

Despite the occurrence of the bundle discharge timing error, the finisher 20 continues carrying the sheets without stopping. Since the takeout of a new sheet by the pickup roller 17 in the MFP 10 is suspended for a predetermined time because of the occurrence of the bundle discharge timing error, printing and hence carrying of the sheet are delayed. However, after a delay of a predetermined time, as the new sheet P3 is taken out from the paper supply unit 16, printing is resumed and sheet carrying in the finisher 20 is continued. Therefore, despite the occurrence of the timing error, the finisher 20 continues sheet finishing without troubling the user.

According to this embodiment, despite that a timing error occurs because of a delay in the operation in the finisher 20, the user does not have to carry out operation to remove the sheet left in the MFP 10. In the case of a timing error of the assist arms 37, the sheet left in the MFP 10 is discharged toward the first tray 21 and therefore the user only removes the sheet P discharged to the first tray 21. In the case of a bundle discharge timing error, printing and sheet finishing are continued without any operation by the user. Thus, maintenance is not needed and there is no waste of sheets.

The invention is not limited to the embodiment, various changes and modifications can be made without departing from the scope of the invention. For example, the structure, operation and the like of the standby unit or the finishing unit of the sheet finisher may be arbitrary, and the number of sheets that can be buffered by the standby unit is not limited. The predetermined time by which the takeout of sheet is delayed in the case of a bundle discharge timing error is not limited, either.

Moreover, the structure of the image forming apparatus is not limited. For example, the image forming apparatus may have both a color printer unit and a monochrome printer unit. In the image forming apparatus having both the color printer unit and the monochrome printer unit, the printing time differs between the two printer units. Therefore, when one job includes a color job and a monochrome job, a timing error may occur. For example, when a monochrome job is carried out following a color job, sheet finishing on the preceding color sheet may become delayed, causing a timing error. In such case, the user's operation to remove the sheet can be significantly reduced and there is no waste of sheets. 

1. A sheet finishing device comprising: a housing unit which houses a sheet discharged from an image forming apparatus; a carrying unit which carries the sheet discharged from the image forming apparatus in a direction of the housing unit; a standby unit which is arranged on a carrying path of the carrying unit and temporarily holds the sheet; a finishing unit which is arranged on the carrying path of the carrying unit and performs finishing of the sheet; and a control unit which, when a carrying error in the carrying unit is a first error, controls the carrying unit to stop and responses the first error to the image forming apparatus, and when the carrying error is a second error, controls the carrying unit to continue driving and responses the second error to the image forming apparatus.
 2. The device of claim 1, wherein the first error is a sheet jam in which the sheet is jammed in the carrying path, and the second error is an operation delay generated on the carrying path.
 3. The device of claim 1, wherein when the carrying error is the second error, the control unit requests a delay request to delay image formation that is to be newly started, to the image forming apparatus.
 4. The device of claim 1, wherein when the carrying error is the second error, the control unit requests a stop request to stop image formation that is to be newly started, to the image forming apparatus.
 5. The device of claim 2, wherein when the carrying unit is controlled to continue driving in the case where the operation delay is an operation delay in the finishing unit, the carrying unit continues carrying the sheet discharged from the image forming apparatus up to the standby unit and stands by the sheet in the standby unit.
 6. The device of claim 5, wherein when the operation delay is an operation delay in the finishing unit, the control unit requests a delay request to delay image formation that is to be newly started, to the image forming apparatus, and the carrying unit continues carrying the sheet discharged from the image forming apparatus by already started image formation up to the standby unit and stands by the sheet in the standby unit.
 7. The device of claim 6, wherein the finishing unit has a supporting unit which is arranged between the standby unit and the housing unit in the carrying path and supports the sheet that is carried directly from the image forming apparatus or carried via the standby unit, and an alignment unit which aligns the sheet on the supporting unit, the carrying unit has a paper discharge unit which discharges the sheet on the supporting unit to the housing unit, and the carrying unit carries the sheet from the standby unit to the supporting unit when paper discharge operation by the paper discharge unit is completed.
 8. The device of claim 7, wherein when the number of sheets standing by in the standby unit exceeds a prescribed number of sheets, an alignment operation by the alignment unit is increased.
 9. The device of claim 6, wherein the delay request delays the image formation that is to be newly started until the finishing unit completes a finishing operation, then resumes new image formation to the image forming apparatus.
 10. The device of claim 2, wherein when the carrying unit is controlled to continue driving in the case where the operation delay is an operation delay in the standby unit, the control unit requests a stop request to stop image formation that is to be newly started, to the image forming apparatus, and the carrying unit carries the sheet discharged from the image forming apparatus by already started image formation, directly to the housing unit.
 11. A sheet carrying method for a sheet finishing device comprising: carrying a sheet discharged from an image forming apparatus in a first direction, with or without a finishing operation; stopping the carrying of the sheet in the first direction and notifying the image forming apparatus of the first error when a carrying error is a first error; and continuing the carrying of the sheet in the first direction and notifying the image forming apparatus of the second error when the carrying error is a second error.
 12. The method of claim 11, wherein the first error is a sheet jam in which the sheet is jammed while the sheet is carried in the first direction, and the second error is an operation delay generated at the time of carrying out the finishing operation of the sheet.
 13. The method of claim 11, wherein when the carrying error is the second error, requesting a delay request to delay image formation that is to be newly started to the image forming apparatus.
 14. The method of claim 11, wherein when the carrying error is the second error, requesting a stop request to stop image formation that is to be newly started to the image forming apparatus.
 15. The method of claim 12, wherein when an operation delay occurs at the time of carrying out the finishing operation of the sheet, when the carrying of the sheet in the first direction is continued, continuing the carrying of the sheet discharged from the image forming apparatus in the first direction to a standby unit and standing by the sheet in the standby unit.
 16. The method of claim 15, wherein when an operation delay occurs at the time of carrying out the finishing operation of the sheet, when the carrying of the sheet in the first direction is continued, requesting a delay request to delay image formation that is to be newly started to the image forming apparatus, and continuing the carrying of the sheet in the first direction discharged from the image forming apparatus by already started image formation to the standby unit and standing by the sheet in the standby unit.
 17. The method of claim 16, wherein when the operation delay is a sheet discharge delay from a supporting unit downstream from the standby unit, carrying the sheet from the standby unit to the supporting unit when the discharge of the sheet from the paper discharge unit is completed.
 18. The method of claim 17, wherein when the number of sheets standing by in the standby unit exceeds a prescribed number of sheets, increasing an operation to align the sheet on the supporting unit.
 19. The method of claim 16, wherein the delay request delays the image formation that is to be newly started until the finishing operation of the sheet is completed, then resumes new image formation to the image forming apparatus.
 20. The method of claim 12, wherein when the operation delay is an operation delay in the standby unit, requesting a stop request to stop image formation that is to be newly started to the image forming apparatus, and carrying the sheet discharged from the image forming apparatus by already started image formation in the first direction and housing directly in a housing unit. 